Operators of cable television systems, also known as Multiple Service Operators (MSOs), continuously make attempts to offer faster service to meet customer demand and competition for better service, yielding higher peak rates year after year. To accommodate higher peak rates, the Data Over Cable Service Interface Specification (DOCSIS) 3.1 specifications were developed and issued in 2013. DOCSIS 3.1 standard promises a great capacity potential by extending the spectrum in both the downstream (DS) and upstream (US) directions. DOCSIS 3.1 extends the spectrum by using, in part, a modern PHY technology (i.e., Orthogonal Frequency Division Multiplexing (OFDM)), and improved Forward Error Correction (FEC) technology (i.e., Low Density Parity Check Codes (LDPC)).
However, upstream (US) resource allocation and scheduling in DOCSIS networks continues to have challenges that are different from those of downstream (DS) scheduling, where the traffic is broadcasted to all modems at once. Issues in the US direction that affect network migration include noise funneling, distortion, burst transmission, topology resolution, multiple access, etc. Further, the migration to DOCSIS 3.1 may be challenging due to differences in technology from DOCSIS 3.0 to DOCSIS 3.1. For example, the migration in the US can be more challenging than the DS due to the limited available spectrum and the potential spectral overlap for DOCSIS 3.1 OFDMA channels and DOCSIS 3.0 Single-Carrier Quadrature Amplitude Modulation (SC-QAM) channels.
In DOCSIS 3.0 and earlier DOCSIS versions, two kinds of channels were supported: TDMA/ATDMA (time division multiple access/advanced time divisional multiple access) and SCDMA (synchronous code division multiple access). For ATDMA, a time-division operation, one cable modem (CM) is allowed to transmit at a time per channel. Each TDMA/ATDMA channel is independent (i.e., frequency division is employed such that each channel operates on a different frequency). For SCDMA channels, multiple cable modems (CM)s can transmit at the same time. Since the bandwidth (BW) allocated to the SCDMA channel is not shared by other channels (i.e., frequency division), different SCDMA channels can be treated independently.
The creation of DOCSIS 3.1 introduced the concept of orthogonal frequency division multiple access (OFDMA) channels which allows simultaneous CM transmissions within a channel and also allows OFDMA channels to overlap with ATDMA channels. This latter feature means that the overlapping part of the spectrum can be used by ATDMA channels for some time and OFDMA channels for some other times (i.e., time division). That is, the ATDMA channels and OFDMA channels have to time-share the overlapped frequency. However, under these circumstances, a channel's US scheduler cannot be completely independent and there is no coordination of transmissions on the overlapping channels.
Improved techniques for coordination and scheduling of overlapping channels in a cable television system, such as overlapping DOCSIS channels, are desirable.
It is noted that while the accompanying FIGs. serve to illustrate embodiments of concepts that include the claimed invention, and explain various principles and advantages of those embodiments, the concepts displayed are not necessary to understand the embodiments of the present invention, as the details depicted in the FIGs. would be readily apparent to those of ordinary skill in the art having the benefit of the description herein.